This book differed from most of the other fish books I've been reading in that it does not go into details about aquarium setup or fish care. Instead, its focus is biology. So I learned some interesting stuff, like that fish scales have annual growth rings, and looked at some fascinating diagrams and photographs- in particular a series showing the growth and development of fish eggs (magnified many times). Although, once again, this is an older book, the science still seems pretty solid. Following the first twenty-five pages of biology lessons and fish anatomy, there are over four hundred photographs of popular aquarium fish. Most are black and white, a handful in color, some small marginal drawings pointing out sexual dimorphism. A lot of the pictures show spawning or parental behavior of the fishes. While many of the descriptions detail the water conditions, food and other particulars each species needs, the author seemed to be more focused on informing the reader about breeding behavior and how to rear the fry. It was only mildly interesting. I really browsed through the majority of the book.